Desorption study of spent activated carbon filter to investigate micropollutants in tap water

Abstract

Desorption of micropollutants such as pharmaceuticals and personal care products (PPCPs) and endocrine disrupting compounds (EDCs) from a spent activated carbon using ultrasonic irradiation and organic solvent extraction were investigated. First, to optimized the desorption condition, this study compared several extraction solvents, appropriate amount of solvent, and sonication time. The optimized condition for desorption of micropollutants was found to be 800 mL of acetonitrile solvent, and 90 min of sonication for 1 g of PAC at 30oC. Then, to examine which micropollutants were adsorbed in the powdered activated carbon (PAC) filter used in the commercial water purifier, this optimized desorption condition was applied to extract the micropollutants from spent PAC filter. Total 11 micropollutants (caffeine, acetaminophen, sulfamethazine, sulfamethoxazole, metoprolol, carbamazepine, naproxen, bisphenol-A, ibuprofen, diclofenac, and triclocarban) were analysed from spent carbon filter. Among the micropollutants, caffeine, metoprolol, naproxen, and diclofenac had higher detection frequencies (>60%), and sulfamethazine, metoprolol and ibuprofen were only detected in the carbon filters, but not in the tap water, indicating that these micropollutants might exist less than detection level in the tap water, but accumulated in the carbon filter. Also, the regional patterns where the water purifiers are used were examined by identifying micropollutant detection patterns from spent carbon filter with various regions in Korea. The result showed that higher concentration of micropollutants were detected from the carbon filter collected from the Han river and Nakdong river basins with large population. Also, the level of micropollutants were higher where advanced oxidation process (AOP) are adopted in the drinking water treatment plants (WTPs), indicating that AOP process is effective for the removal of micropollutants. When compared according to different pore size filters, the desorption amount was higher from the filter which pore size is 10 times smaller than the other, indicating that higher amount of micropollutants can be adsorbed in smaller pore size filter.